Neural crest (NC) cells are an embryonic, multipotent population of stem cells that arise from the lateral edges of the neural plate. Once the neural plate has formed the neural tube, NC migrate away from the dorsal neural tube to contribute to a wide variety of neuronal and non-neuronal tissues, including cells of the heart, peripheral nervous system, enteric nervous system, craniofacial cartilage, and pigmented cells. The proposed studies are aimed at understanding the processes that govern the establishment of the premigratory NC population in the zebrafish (Danio rerio). This is important because mutations that reduce the number of premigratory NC have defects in formation of differentiated tissues (e.g., the splotch/pax-3 mouse mutant). Also perturbations in NC development are a major component of human congenital syndromes involving craniofacial, heart, and enteric nervous system development. The generation of premigratory NC has been proposed to be a multistep process involving induction of a precursor population followed by its proliferative expansion. Bone morphogenetic proteins (Bmps), fibroblast growth factors (Fgfs), and Wnts are growth factors important for generating the final number of premigratory NC population. However, their precise roles in the processes of early NC induction and proliferation are not well understood. I will combine experimental embryology with genetic manipulations in the zebrafish to 1. establish assays that differentiate between induction and proliferation of early NC cells 2. test whether Bmps, Fgf, and Wnts affect induction and/or proliferation, and 3. characterize the role and identity of a new gene, alyron (aln) that is required for the generating the premigratory NC population.